Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka, 560-0043 Japan.
Plant Cell Physiol. 2013 Jan;54(1):93-106. doi: 10.1093/pcp/pcs160. Epub 2012 Dec 4.
Aureochrome-1 (AUREO1) is a blue light (BL) receptor that mediates the branching response in the stramenopile alga, Vaucheria frigida. AUREO1 harbors a basic leucine zipper (bZIP) domain at the N-terminus and a light-oxygen-voltage-sensing (LOV) domain within the C-terminal region, and has been suggested to function as a light-regulated transcription factor. To understand the molecular mechanism of AUREO1, we have prepared three recombinant proteins: a full-length AUREO1 (FL), an N-terminal truncated construct containing bZIP and LOV (ZL) and a LOV-only (LOV) construct. The constructs showed the same absorption and fluorescent spectra in the dark state and underwent the characteristic cyclic reaction as previously observed in LOV domains upon BL excitation. FL and ZL bound to DNA in a sequence-specific manner. BL appeared to induce a shift of the α-helical structure of the LOV domain to a β-sheet structure, but did not alter the hydrodynamic radius (R(H)) of this domain. ZL formed a dimer possibly through disulfide linkages in the bZIP and the linker region between bZIP and LOV. BL induced an approximately 5% increase in the R(H) of ZL, although its secondary structure was unchanged. These results support a schema where BL-induced changes in the LOV domain may cause conformational changes in the bZIP and/or the linker of a dimeric ZL molecule. Since a 5% increase of the R(H) was also observed with the FL construct, BL may induce global conformational changes similar to those observed for ZL, and formation of the FL dimer may facilitate DNA binding.
Aureochrome-1 (AUREO1) 是一种蓝光 (BL) 受体，可介导丝藻门藻类 Vaucheria frigida 的分支反应。AUREO1 的 N 端含有碱性亮氨酸拉链 (bZIP) 结构域，C 端含有光氧电压感受结构域 (LOV)，被认为是一种光调控转录因子。为了理解 AUREO1 的分子机制，我们制备了三种重组蛋白：全长 AUREO1 (FL)、含有 bZIP 和 LOV 的 N 端截断构建体 (ZL) 和仅 LOV (LOV) 构建体。在黑暗状态下，这些构建体表现出相同的吸收和荧光光谱，并在 BL 激发后表现出与 LOV 结构域先前观察到的特征循环反应。FL 和 ZL 以序列特异性方式结合 DNA。BL 似乎诱导 LOV 结构域的α螺旋结构向β折叠结构转变，但不改变该结构域的流体力学半径 (R(H))。ZL 可能通过 bZIP 中的二硫键和 bZIP 与 LOV 之间的连接区形成二聚体。BL 诱导 ZL 的 R(H) 增加约 5%，尽管其二级结构保持不变。这些结果支持 BL 诱导 LOV 结构域变化可能导致二聚体 ZL 的 bZIP 和/或连接区构象变化的方案。由于 FL 构建体也观察到 R(H) 增加 5%，BL 可能诱导类似于 ZL 观察到的全局构象变化，并且 FL 二聚体的形成可能有助于 DNA 结合。
